Threat: A short-range Ghazanvi missile is launched from an undisclosed location in Pakistan in 2008 (file pic)

The United States has 'deep concerns' about the safety and security of Pakistan's nuclear weapons programme, leaked diplomatic documents have suggested.

Documents from the latest cache of leaked U.S. cables demonstrate that America and the UK have similar anxieties about Islamabad's nuclear arsenal.

U.S. officials are quoted citing the danger of Pakistani fissile material finding its way into the hands of extremists.

The UK's concerns were communicated to the U.S. by Mariot Leslie, then the Foreign Office's director general of defence and intelligence, at a meeting in September last year.

Now Britain's permanent representative to Nato, she is quoted as saying that 'the UK has deep concerns about the safety and security of Pakistan's nuclear weapons'.

She goes on to say that China could play a 'big role' in 'stabilising Pakistan'.

The Ministry of Defence's director general for security policy, Jon Day, warned U.S. officials separately that relations between Pakistan and India were especially strained.

He expressed support for the encouragement of a 'cold-war'-like relationship' between the two countries that would 'introduce a degree of certainty'.

He apparently went on to say that Pakistan was 'not going in a good direction'.

The disclosures could test relations between Britain and Pakistan, a vitally important regional ally and neighbour of Afghanistan.

The Foreign Office said it would not comment on the detail of the documents obtained by whistle-blowing website WikiLeaks and published tonight by the Guardian.

Fears: America and Britain are both said to have 'deep concerns' over Pakistan's weapons programme, according to leaked cables

Pakistan army's plan to oust leader

The general at the top of Pakistan's army proposed to topple President Asif Ali Zadari during internal wrangling last year, WikiLeaks has revealed.

General Ashfaq Kayani, floated the idea during meetings with the U.S. Ambassador in March 2009 as thousands of supporters of opposition leader Nawaz Sharif took to the streets.

In an apparent solution that would stop the opposition leader coming to power, the army chief said he would reluctantly persuade the President to resign and replace him with Asfandyar Wali Khan, leader of the Pushtun Awami National Party.

As a result 'this would not be a formal coup,' US Ambassador Anne Patterson noted but would leave in place a government.

However, the plan did not go ahead and Zadari was forced into a humiliating climbdown having mobilised supporters.

The WikiLeaks documents also reveal that British Ambassador Robert Brindle was working to find his own solution and demonstrate the roles of both western diplomats and the army in Pakistan's volatile politics.

Tories say: 'we don't depend on Pakistani votes'

Liam Fox: We don't depend on Pakistani votes domestically

The Conservatives promised the U.S. before the election that they would be tougher on Pakistan - because unlike Labour they did not depend on votes from people with Pakistani connections.

Liam Fox, who is now defence secretary, criticised Labour for their pro-Pakistan approach in cables given to WikiLeaks.

David Cameron has apparently has apparently shifted the UK's stance towards Pakistan since he was elected.

He visited India on a trade mission in June before telling Pakistan 'not to face both ways' when it came to tackling terrorism.

US ambassador to the UK Louis Susman was told that 'the Conservatives are "less dependant" than the Labour party on votes from the British-Pakistani community.'

Mr Susman added in the cable: 'Fox criticised the Labour government for policies which reinforce the Indian government's long-held view that HMG's (Her Majesty's Government) foreign relations on the subcontinent are "skewed to Pakistan".'

Separately David Cameron told Richard Holbrooke, the U.S. special envoy to Afghnaistan and Pakistan, that the Labour goverment 'let in some crazies'.

The Conservative leader said that the government had got it wrong on immigration and let in the wrong sort of people before realising what was going wrong.

Mr Holbrooke reported to Washington: 'On the radicalisation of British Pakistanis, Cameron said the UK had 'gotten it wrong domestically'... he argued that PM Brown's policy had been too willing to engage with radicalised but non-violent Muslim groups... "We let in some crazies," Cameron said, "and didn't wake up soon enough".'